Municipal Waste

Municipal solid waste is a porous material consisting of a solid skeleton with several components and a pore space.

Zusammensetzung des Siedlungsabfalls

Granular, soil-like particles can be distinguished from elongate, fibrous particles. Furthermore, the solid matter may be divided with respect to biological degradability to inert matter, organic matter and biomass in general. Two fluid phases, leachate and landfill gas, fill the pore space. Both fluid phases contain several chemical substances, whereas the composition changes due to ongoing degradation and physical exchange processes.

Biological degradation and heat generation

Chemische Prozesse im Siedlungsabfall

In landfills, degradation proceeds mainly under anaerobic conditions. Degradation models of varying complexity may be incorporated into the coupled description of THMC processes by mass exchange terms. 
In step R1, organic matter DO reacts with water to acetic acid and carbon dioxide. The reaction is accompanied by the growth of biomass. In step R2 acetic acid reacts to water, carbon dioxide, methane and biomass as well. Step L describes the lysis of biomass. Evaporation, condensation and dissolution are considered as well and denoted by P1 and P2, respectively.

Transport properties

Theorie poröser Medien beim Siedlungsabfall

Waste is a porous medium with liquid phase and gas phase filling the pore space. Due to drainage, the waste is likely to be unsaturated at most times. Considering that the fluid phases of MSW are composed of several components, multiphasic, multicomponent convective transport is modeled by means of a generalized Darcy’s law, which covers unsaturated flow by introducing relative permeabilities and dynamic viscosities.

Mechanical behaviour

The material model treats MSW as a composite. Thereby, the solid phase is supposed to consist of a soil-like basic matrix and embedded fibres.

Siedlungsabfall als Komposit

In experiments a particular hardening phenomenon is observed as the friction angle tends to increase at high compression, which is attributed to the reinforcing effect of the fibrous particles in the waste. Time dependent settlements have to be covered as well as anisotropies due to emplacement strategies. An important question is, e.g., to which extent the loss of solid matter is transferred to additional settlement.

Setzungsverhalten des Siedlungsabfalls über die Zeit

Completed Research Projects

  • S. Bente: Interaction of Degradation, Deformation and Transport Processes in Municipal Solid Waste Landfills, Dissertation, TU Braunschweig, 2010
  • V.Krase: Stability of Municipal Solid Waste Landfills, Dissertation, TU Braunschweig, 2008
  • J. Ebers-Ernst: Modellierung des inelastischen Verformungsverhaltens von Siedlungsabfalldeponien, Dissertation, TU Braunschweig, 2001